    var gl;
    function initGL(canvas) {
        try {
            gl = canvas.getContext("experimental-webgl");
            gl.viewportWidth = canvas.width;
            gl.viewportHeight = canvas.height;
        } catch (e) {
        }
        if (!gl) {
            alert("Could not initialise WebGL, sorry :-(");
        }
    }
 
 
    function getShader(gl, id) {
        var shaderScript = document.getElementById(id);
        if (!shaderScript) {
            return null;
        }
 
        var str = "";
        var k = shaderScript.firstChild;
        while (k) {
            if (k.nodeType == 3) {				//3代表文本节点
                str += k.textContent;
            }
            k = k.nextSibling;
        }
 
        var shader;
        if (shaderScript.type == "x-shader/x-fragment") {
            shader = gl.createShader(gl.FRAGMENT_SHADER);
        } else if (shaderScript.type == "x-shader/x-vertex") {
            shader = gl.createShader(gl.VERTEX_SHADER);
        } else {
            return null;
        }
 
        gl.shaderSource(shader, str);
        gl.compileShader(shader);
 
        if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
            alert(gl.getShaderInfoLog(shader));
            return null;
        }
 
        return shader;
    }
 
 	/*----定义存储数据的矩阵堆栈----*/
	var mvMatrix = mat4.create();
    var mvMatrixStack = [];
    var pMatrix = mat4.create();
 	 
	 function mvPushMatrix() {
        var copy = mat4.create();
        mat4.set(mvMatrix, copy);
        mvMatrixStack.push(copy);
    }
 
    function mvPopMatrix() {
        if (mvMatrixStack.length == 0) {
            throw "Invalid popMatrix!";
        }
        mvMatrix = mvMatrixStack.pop();
    }
	
    var shaderProgram;
 
    function initShaders(){
		var fragmentShader = getShader(gl, "shader-fs");
		var vertexShader = getShader(gl, "shader-vs");
		
		shaderProgram = gl.createProgram();
		gl.attachShader(shaderProgram, vertexShader);
		gl.attachShader(shaderProgram, fragmentShader);
		gl.linkProgram(shaderProgram);
		
		if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
			alert("Could not initialise shaders");
		}
		
		gl.useProgram(shaderProgram);
		
		shaderProgram.vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
		gl.enableVertexAttribArray(shaderProgram.vertexPositionAttribute);
		
		shaderProgram.textureCoordAttribute = gl.getAttribLocation(shaderProgram, "aTextureCoord");
        gl.enableVertexAttribArray(shaderProgram.textureCoordAttribute);
		
		shaderProgram.samplerUniform = gl.getUniformLocation(shaderProgram, "uSampler");
		
		shaderProgram.pMatrixUniform = gl.getUniformLocation(shaderProgram, "uPMatrix");
		shaderProgram.mvMatrixUniform = gl.getUniformLocation(shaderProgram, "uMVMatrix");
	}
 
 
  function handleLoadedTexture(texture) {
        gl.bindTexture(gl.TEXTURE_2D, texture);
        gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);
		//上传到显卡端的纹理空间
        gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, texture.image);
       //放大和缩小纹理
	    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
        gl.bindTexture(gl.TEXTURE_2D, null);
    }
 
 
    var neheTexture;
 	
	//初始化纹理的函数
    function initTexture() {
        neheTexture = gl.createTexture();
		//纹理对象的属性添加js的图片对象
        neheTexture.image = new Image();
        neheTexture.image.onload = function () {
            handleLoadedTexture(neheTexture)
        }
 
        neheTexture.image.src = "../images/nehe.gif";
    }
    function setMatrixUniforms() {  //mvMatrix变量来进行任何移动和旋转，只存在于Javascript,setMatrixUniforms将这些操作推送到显卡中去。
        gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, pMatrix);
        gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, mvMatrix);
    }
 
 
 
    var cubeVertexPositionBuffer;
    var cubeVertexColorBuffer;
    var cubeVertexIndexBuffer;
 
    function initBuffers() {
		
       pyramidVertexPositionBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexPositionBuffer);
        var vertices = [
            // Front face
             0.0,  1.0,  0.0,
            -1.0, -1.0,  1.0,
             1.0, -1.0,  1.0,
 
            // Right face
             0.0,  1.0,  0.0,
             1.0, -1.0,  1.0,
             1.0, -1.0, -1.0,
 
            // Back face
             0.0,  1.0,  0.0,
             1.0, -1.0, -1.0,
            -1.0, -1.0, -1.0,
 
            // Left face
             0.0,  1.0,  0.0,
            -1.0, -1.0, -1.0,
            -1.0, -1.0,  1.0
        ];
		
		gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
		pyramidVertexPositionBuffer.itemSize=3;
		pyramidVertexPositionBuffer.numItems=12;
		
		
		//椎体颜色矩阵
		pyramidVertexColorBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexColorBuffer);
        var colors = [
            // Front face
            1.0, 0.0, 0.0, 1.0,
            0.0, 1.0, 0.0, 1.0,
            0.0, 0.0, 1.0, 1.0,
 
            // Right face
            1.0, 0.0, 0.0, 1.0,
            0.0, 0.0, 1.0, 1.0,
            0.0, 1.0, 0.0, 1.0,
 
            // Back face
            1.0, 0.0, 0.0, 1.0,
            0.0, 1.0, 0.0, 1.0,
            0.0, 0.0, 1.0, 1.0,
 
            // Left face
            1.0, 0.0, 0.0, 1.0,
            0.0, 0.0, 1.0, 1.0,
            0.0, 1.0, 0.0, 1.0
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);
        pyramidVertexColorBuffer.itemSize = 4;
        pyramidVertexColorBuffer.numItems = 12;
		
		
		
		//立方体位置数组
		cubeVertexPositionBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
        vertices = [
            // Front face
            -1.0, -1.0,  1.0,
             1.0, -1.0,  1.0,
             1.0,  1.0,  1.0,
            -1.0,  1.0,  1.0,
 
            // Back face
            -1.0, -1.0, -1.0,
            -1.0,  1.0, -1.0,
             1.0,  1.0, -1.0,
             1.0, -1.0, -1.0,
 
            // Top face
            -1.0,  1.0, -1.0,
            -1.0,  1.0,  1.0,
             1.0,  1.0,  1.0,
             1.0,  1.0, -1.0,
 
            // Bottom face
            -1.0, -1.0, -1.0,
             1.0, -1.0, -1.0,
             1.0, -1.0,  1.0,
            -1.0, -1.0,  1.0,
 
            // Right face
             1.0, -1.0, -1.0,
             1.0,  1.0, -1.0,
             1.0,  1.0,  1.0,
             1.0, -1.0,  1.0,
 
            // Left face
            -1.0, -1.0, -1.0,
            -1.0, -1.0,  1.0,
            -1.0,  1.0,  1.0,
            -1.0,  1.0, -1.0
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
        cubeVertexPositionBuffer.itemSize = 3;
        cubeVertexPositionBuffer.numItems = 24;
		
		//立方体颜色数组
		cubeVertexTextureCoordBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexTextureCoordBuffer);
        var textureCoords = [
          // Front face
          0.0, 0.0,
          1.0, 0.0,
          1.0, 1.0,
          0.0, 1.0,
 
          // Back face
          1.0, 0.0,
          1.0, 1.0,
          0.0, 1.0,
          0.0, 0.0,
 
          // Top face
          0.0, 1.0,
          0.0, 0.0,
          1.0, 0.0,
          1.0, 1.0,
 
          // Bottom face
          1.0, 1.0,
          0.0, 1.0,
          0.0, 0.0,
          1.0, 0.0,
 
          // Right face
          1.0, 0.0,
          1.0, 1.0,
          0.0, 1.0,
          0.0, 0.0,
 
          // Left face
          0.0, 0.0,
          1.0, 0.0,
          1.0, 1.0,
          0.0, 1.0,
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoords), gl.STATIC_DRAW);
        cubeVertexTextureCoordBuffer.itemSize = 2;
        cubeVertexTextureCoordBuffer.numItems = 24;
      
		
		
 		cubeVertexIndexBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);  //gl.ELEMENT_ARRAY_BUFFER，用于指定这是一个用于存放索引数据的缓存对象
        var cubeVertexIndices = [
            0, 1, 2,      0, 2, 3,    // Front face  012为一个三角形，023为一个三角形，之后0123为一个正方形
            4, 5, 6,      4, 6, 7,    // Back face
            8, 9, 10,     8, 10, 11,  // Top face
            12, 13, 14,   12, 14, 15, // Bottom face
            16, 17, 18,   16, 18, 19, // Right face
            20, 21, 22,   20, 22, 23  // Left face
        ];
        gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(cubeVertexIndices), gl.STATIC_DRAW);
        cubeVertexIndexBuffer.itemSize = 1;
        cubeVertexIndexBuffer.numItems = 36;
        
    }
 
	/*定义转动的角度----*/ 
	
 	var rPyramid = 0;
    var rCube = 0;
	
	/*角度变成弧度*/
	function degToRad(degrees){
		return degrees*Math.PI/180;
	}
	
	 var xRot = 0;
    var yRot = 0;
    var zRot = 0;
	
    function drawScene() {
        //gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
     	
		gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
 		
	/*---视野是45°、canvas的宽高比以及从我们的视点看到的最近距离是0.1个单位，最远距离是100个单位---*/
        mat4.perspective(45, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0, pMatrix);
 
        mat4.identity(mvMatrix);
        mat4.translate(mvMatrix, [-1.5, 0.0, -7.0]);
        
		/*mvPushMatrix();
		mat4.rotate(mvMatrix, degToRad(rPyramid), [0, 1, 0]);
		
		gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexPositionBuffer);
        gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, pyramidVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
 
        gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexColorBuffer);
        gl.vertexAttribPointer(shaderProgram.vertexColorAttribute, pyramidVertexColorBuffer.itemSize, gl.FLOAT, false, 0, 0);
 
        setMatrixUniforms();
        gl.drawArrays(gl.TRIANGLES, 0, pyramidVertexPositionBuffer.numItems);
 		
		mvPopMatrix();*/
		
		
        //绘制立方体  后面坐标表示立方体的位置
        mat4.translate(mvMatrix, [1.5, 0.0, 0.0]);
        
		 
        mat4.rotate(mvMatrix, degToRad(xRot), [1, 0, 0]);
        mat4.rotate(mvMatrix, degToRad(yRot), [0, 1, 0]);
        mat4.rotate(mvMatrix, degToRad(zRot), [0, 0, 1]);
 
        gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
        gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, cubeVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
 		/*它绑定到合适的属性中，着色器可以调用*/
        gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexTextureCoordBuffer);
        gl.vertexAttribPointer(shaderProgram.textureCoordAttribute, cubeVertexTextureCoordBuffer.itemSize, gl.FLOAT, false, 0, 0);
 
        gl.activeTexture(gl.TEXTURE0);
        gl.bindTexture(gl.TEXTURE_2D, neheTexture);
        gl.uniform1i(shaderProgram.samplerUniform, 0);
 
		
		gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
        setMatrixUniforms();
        gl.drawElements(gl.TRIANGLES, cubeVertexIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0);
	}
    
	/*角度根据时间产生变化*/
	 var lastTime = 0;
 
    function animate() {
        var timeNow = new Date().getTime();
        if (lastTime != 0) {
            var elapsed = timeNow - lastTime;
 
            xRot += (90 * elapsed) / 1000.0;
            yRot += (90 * elapsed) / 1000.0;
            zRot += (90 * elapsed) / 1000.0;
        }
        lastTime = timeNow;
    }
  	
 
    function webGLStart() {
        var canvas = document.getElementById("lesson04-canvas");
        initGL(canvas);
        initShaders();
        initBuffers();
		
		//启动纹理的效果
 		initTexture();
        gl.clearColor(1.0, 1.0, 1.0, 1.0);
        gl.enable(gl.DEPTH_TEST);

		/*
		 * 启动动画效果
		 */
		tick();
		
		
    }

	
	function tick(){
		requestAnimFrame(tick);
		drawScene();
		animate();
		
	}
	
	
	
	
	
	
	
